The present disclosure relates to an organic electroluminescence (EL) display panel in which organic EL elements utilizing an electroluminescence phenomenon of an organic material are used, and a method of manufacturing the same.
In recent years, as display panels for use in display apparatuses such as digital television sets, organic EL display panels in which a plurality of organic EL elements are arranged in a matrix pattern on a substrate have been put to practical use.
In an organic EL display panel, generally, a light-emitting layer of each organic EL element and those of the adjacent organic EL elements are partitioned by an insulating layer formed of an insulating material. In an organic EL display panel for color display, the organic EL elements constitute sub-pixels that each emit light in red (R), green (G) or blue (B), and the adjacent RGB sub-pixels are combined together to form a unit pixel in color display.
The organic EL element has a basic structure in which a light-emitting layer containing an organic light-emitting material is disposed between a pair of electrodes, namely, an anode and a cathode. At the time of driving, a voltage is impressed between the pair of electrodes, and holes injected into the light-emitting layer from the anode and electrons injected into the light-emitting layer from the cathode are brought into recombination, whereby light is emitted. In a top emission type organic EL element, the light from the light-emitting layer is reflected by the anode which is formed of a light-reflecting material and is emitted to the upper side from the cathode which is formed of a light-transmitting material.
For enhancing the light emission efficiency of the organic EL element, it is important to efficiently inject the carriers (holes and electrons) from the electrodes into the functional layer. For efficient injection of the carriers, in general, it is effective to provide an injection layer for lowering the energy barrier at the time of injection (injection barrier), between each electrode and the functional layer. For instance, in relation to a top emission type organic EL element, there has been proposed a technology in which a plurality of hole injection layers are provided between the anode and the light-emitting layer to enhance the hole injection property from the anode into the light-emitting layer, thereby improving the life characteristic of the organic EL element (see, for example, Japanese Patent Laid-open No. 2007-5784).